Conventionally, a pipe of a single structure is normally used as a pipe through which fluid such as gas flows from a gas source to a turbine. There is a pipe of a double pipe structure in which a pipe is disposed inside another pipe, the inside pipe (hereinafter, referred to as inner pipe,) is inserted into the outside pipe (hereinafter, referred to as outer pipe) in a state where a predetermined gap is held between the inner and outer pipes, two kinds of gases sent from an upstream location such as a supply source path through the outer pipe and the inner pipe, and the gases are supplied to a downstream location such as a predetermined discharging destination (Patent Document 1).
The double pipe structure, for example, is also used in a piping system in spent nuclear fuel processing facility, radioactive-waste treatment facility, and nuclear power facility (Patent Documents 2 and 3).
Patent Document 1 The Publication of Japanese Patent No. 3971683
Patent Document 2 Japanese Unexamined Patent Application, Publication No. H09-54189
Patent Document 3 Japanese Unexamined Patent Application, Publication No 0.2003-294883